Centrifuges have been employed consisting of rapidly revolving rotors with one or more chambers near the periphery for receiving cells with sector-shaped cavities containing samples to be centrifuged and to be examined photoelectrically during the centrifuging action. Such rotors are provided with an even number of diametrically opposite chambers for symmetry to prevent unbalance during the rotation and there may be an odd number of cells in the chambers. The otherwise unbalanced cell is counterbalanced by the provision of a counterbalance in the chamber diametrically opposite it. The chambers are cylindrical with axes parallel to the axis of the rotor and the cells received in the chambers have sector-shaped cavities to hold samples. The rotors and the cells are so constructed as to provide light paths parallel to the rotor axis extending through the cell and the rotor. These light paths are provided to permit photoelectric measurement or control devices to be employed for measuring or monitoring the variation in density of the centrifuged sample as the heavier material therein is thrown outward during the rapid rotation of the centrifuge rotor. It is necessary, therefore, that the sector-shaped cavities of the cells be accurately aligned angularly in the rotor chambers with respect to the cylindrical axis of the chamber so as to be aligned radially with respect to the axis of rotation of the rotor. If the counterweights have openings for a light beam to be used for timing or other purposes, such openings must also be in radial alignment with respect to the rotor axis of rotation.
One of the methods of angular alignment of the cells and counterweights has been employment of a microscope mounted on a suitable jig or tool fitting the rotor and having cross hairs for alignment with markings on the cell or the counterweight for enabling an operator to align the cell or counterweight by manually turning it until the marking in question and the microscope cross hair are in alignment.
It is an object of the invention to provide a simplified method for alignment of the cells and counterweights which enables the alignment to be accomplished more easily, requiring less care and skill on the part of the operator and avoiding the necessity for the acquisition and use of relatively expensive specially built microscopes and supporting structure therefor fitting the particular centrifuge rotor for which it is designed.
Other and further objects, features and advantages of the invention will become apparent as the description proceeds.